Typically, a base station of a mobile communication system has been divided into a base station main body apparatus for processing a transmitting and receiving signal and an antenna apparatus including a plurality of radiating elements to transmit and receive radio signals. Generally, the base station main body apparatus is installed at a low-lying land on the ground and the antenna apparatus is installed at high positions such as a building roof and a tower. The base station main body apparatus and the antenna apparatus may be connected to each other through a feed cable or the like.
In addition, in the current mobile communication environment, 2 generation (2G), 3G, and 4G long term evolution (LTE) have not only been commercialized, but the introduction of the next generation 5G system has also been considered. Accordingly, various frequency bands of mobile communication services are mixed according to the communication systems or service providers and countries, and the base station environment is also diversified. Accordingly, since the communication environment has service bands frequently changed for each specific service provider, in order to realize an efficient base station system and to reduce the operating cost of the base station, the base station (and base station antenna apparatus) constructs a broadband system capable of covering various service bands.
Meanwhile, in the mobile communication services using a radio wave, there may be areas to which the radio wave cannot be transmitted according to the environment, such as terrains and buildings, due to characteristics of the radio wave. Therefore, recently, a compact antenna apparatus is installed on an outer wall of a building, or the like at a low-lying land on the ground in order to remove a shaded area where the radio wave cannot be transmitted according to the environment. In addition, in the compact antenna apparatuses installed on an outer wall or the like at a low-lying land on the ground are installed with radiating elements having at least one of high frequency bands.
As the compact antenna apparatus for the mobile communication base station is installed at a low-lying land, in appearance, the compact antenna apparatus should not have a size at which a user may feel uncomfortable, etc. That is, in the compact antenna apparatus, a size of a radome provided with the radiating element cannot but be relatively small, and therefore the compact antenna apparatus has a problem in that a space for an automatic tilting module for automatically adjusting a tilting angle of the radiating element like a large antenna apparatus may not be secured.
In addition, the compact antenna apparatuses are greatly affected by buildings and terrains due to the high frequency band and therefore should be installed in a lot of places. However, there may be the problem that the installation of the automatic tilting module in each compact antenna apparatus requires high additional expenses.
In addition, since the size of the radome is small in the compact antenna apparatus, the number of radiating elements installed in the compact antenna apparatus should be inevitably much smaller than that of the large antenna apparatus. For example, compared to the number of radiating elements installed in a large antenna apparatus installed on an outer wall of a high-rise building, the number of radiating elements installed in the large antenna apparatus are about ⅓ or less. If the angle is adjusted by automatically tilting a small number of radiating elements installed in the radome, the tilting angle of the radiating element installed in the compact antenna apparatus is smaller than that of the radiating element of the large antenna apparatus. That is, if the tilting angle of the radiating element is automatically adjusted, the radiating element of the compact antenna apparatus has a problem in that an error range of the tilting angle becomes large. In addition, the compact antenna apparatus is implemented as a high frequency band. If the error of the tilting angle becomes large, there may arise a problem in that the frequency band may be changed, radiation performance may be degraded, the radiation performance may not be realized properly, or the like. Further, if the antenna apparatus is installed on the high outer wall, it is difficult for an operator to manually adjust the tilting angle of the radiating element. However, in the case of the compact antenna installed on a low outer wall or a low-lying land, there is a need for an operator to more easily adjust the tilting angle of the radiating element than the automated tilting operation.